1. Field of the Invention
The present invention relates to a flow-through type electrode assembly such as a hydrogen peroxide electrode, and more particularly, to an electrode construction of an improved configuration.
2. Description of Related Art
Flow-through type enzyme electrodes are known in the prior art as shown in FIG. 3. A sample liquid passage 32 is formed in a block member 31 of synthetic resins. An enzyme electrode 33 and a temperature compensating electrode 34 is disposed in the block number 31 so as to face the sample liquid passage 32. An upper space is provided above the enzyme electrode 33 and below a diaphragm 36 to provide an electrode reaction chamber 35 so that basic substances contained in the sample liquid flowing through the sample liquid passage 32 can be measured in a batch manner. This arrangement has been known as a so-called enzyme electrode (an electrode for measuring hydrogen peroxide and the like with enzymes as media), and is useful for measuring basic substances contained in a sample liquid.
The above-described enzyme electrode 33 can comprise an anode 38, shown in FIG. 4, formed of platinum and disposed almost at a center of an electrode body 37 formed of synthetic resins. A cathode 40 formed of a silver-silver chloride is disposed concentrically with the anode 38 extending through the cathode 40 and through an insulating layer 39. Both the anode 38 and the cathode 40 are advantageously integrally formed, and an enzyme-fixing membrane 41 extends over both the anode 38 and the cathode 40 and is fixed in position by an O-ring 41.
An enzyme electrode 33 having the above-described construction is characterized in that the desired basic substances can be measured by the use of a very small quantity of sample liquid. A disadvantage has occurred, however, in that when the volume of the electrode reaction portion 35 is increased, any small quantity of a basic substance contained within a small quantity of sample liquid is difficult to detect. If the electrode area (liquid-contacting area) of the anode 38 and cathode 40 are reduced in an effort to reduce the volume of the electrode reaction chamber 35, the liquid-contacting area of the anode 38, which is the working electrode, presents a limitation as to the amount of possible reduction in size. As a result, it is also difficult to detect basic substances contained in a very small quantity.
In addition, a disadvantage also occurs in a hydrogen peroxide electrode having almost the same construction as that of the above-described enzyme electrode 33, that is, a construction in which the enzyme-fixing membrane 38 is removed from the constituent members of the enzyme electrode 33. Thus, there is a need in the prior art to provide an improved electrode assembly that resolves the above problems.